1. Field of the Invention
This invention relates to a method of producing metal particles of spherical shape or a shape closely similar to a sphere, more particularly, the present invention aims to produce large amount of spherical metal particles of relatively small and uniform diameter (0.1 to 3.0 mm) by using an apparatus of simplified construction.
2. Prior Art
Heretofore, there has been a method of making spherical metal particles as disclosed in Japanese Unexamined (Laid-Open) Patent Publication No. Sho 58 (1983)-52408. The publication discloses a method, in which the forward tip end of a metal bar is melted by heating while it is rotated at high speed of rotation, thereby a part of the molten metal is scattered to a surrounding atmosphere forming a number of droplets then each of thus scattered droplets of molten metal will solidify being cooled by the atmosphere while they also take spherical form due to surface tension, thereby a large number of metal particles of spherical shape or similar configuration are produced.
However, the size of the metal particles obtained by the aforesaid method is liable to be varied considerably.
There is also a method which appears similar to the present invention with respect to the technical concept of forming particles, that is, the method and apparatus for making flake-like particles disclosed by Japanese Unexamined (Laid-Open) Patent Publication No. Sho 54 (1979)-60262. However, such a method of making metal flakes according to the above-mentioned publication differs entirely from the technical concept of the present invention, because the disclosed method uses a heat extracting circular disc made of a material having high heat transfer coefficient and carrying thereon a large number of teeth or serrations, onto which molten material is adhered to form flake-like particles which are then solidified at least partly by removing their heat by the heat extracting circular disc, subsequently thus solidified flake particles leave from the serrations so as to be cooled into discrete flake particles.
3. Objects of the Invention
The inventor of the present invention intended to produce spherical metal particles by a method different from those methods of making metal particles mentioned above and has been accomplished by this invention.
An object of this invention is to provide a method of producing a large number of spherical metal particles of relatively small size in a continuous manner by making use of a property of a drop of molten metal which is apt to take the form of a sphere due to its surface tension and by relying on the steps of intermittently scattering a predetermined amount of molten metal into the surrounding atmosphere by a rotary drum, each scattered droplet of molten metal to solidify while being cooled by the atmosphere and to be sphere due to the surface tension of the droplet itself. Another object of the invention is to provide metal particles of uniform particle size.
4. Summary of the Invention
The present method utilises an apparatus for producing spherical metal particles comprising, a molten metal reservoir to contain a molten metal, a rotary drum carrying a plurality of teeth or serrations around its outer periphery on which the molten metal is to be adhered and a driving means for rotating the rotary drum at a speed that the molten metal adhered to each serration can successively be scattered by centrifugal force before even a part thereof solidifies.
In other words, the present invention produces metal particles of uniform diameter by successively dipping the tooth or serration disposed around the outer periphery of the drum into the molten metal contained in the reservoir, scattering the molten metal adhered to each tooth or serration one after another as a droplet, by the centrifugal force caused by the rotation of the drum, before even a part of the adhered metal solidifies, cooling the thus scattered molten metal by the atmosphere during its flight to solidify while allowing each droplet to become spherical or closely similar configuration having substantially uniform particle diameter.
According to the present invention, molten metal in the reservoir adheres to each of the teeth or serrations formed around the rotary drum, one after another, thus the amount of the molten metal which determines the diameter of the metal sphere when solidified can be decided by the uniform surface area of the serrations.